汽车专业外语03ppt课件.ppt

,Valve Train and Variable Valve Timing 气门机构与可变气门正时,Unit 3,Passage A,Whats the function of a valve train?,If cylinder heads are the heart of an engine, then the valve train have to be the brains of the operation. Timing the opening, closing, lifting and duration of each valve event is central to increase power and torque.,Passage A,Valve Train 气门机构,Passage A,Valve Train 气门机构,Passage A,Camshaft Valve Valve springs Rocker arms Valve lifter Pushrod,凸轮轴 气门 气门弹簧 摇臂 气门挺杆 推杆,How many parts does a valve train include typically?,Passage A,Valve Train 气门机构,Passage A,http:/www.motorera.com/dictionary/va.htm,Passage A,Camshaft 凸轮轴,Passage A,Rotating shaft with lobes (cams), opening and closing the intake and exhaust valves. When the cam pushes against the lifter, the lifter in turn pushes the valve. When the cam rotates away from the lifter, the valve is closed by a spring that is attached to the valve. Synchronized with the crankshaft (One revolution for every two revolutions of crankshaft),Passage A,Valve 气门,Passage A,Material: Steel alloy, such as steel and nickel, or steel and silicon Withstand extremely high temperature up to 815 (815 degree Celsius) The valve face must seat evenly against the valve seat to prevent leaks. Whats the angle between the valve faces and seats normally?,Passage A,Valve springs 气门弹簧,Passage A,Return the valves to their closed position after opening Need to be very strong to keep the valves in contact with rocker arms,http:/www.corvettefever.com/howto/corp_0701_rocker_arms/photo_01.html,What is the condition of the valve spring? Compressed or extruded?,Passage A,Rocker arms 摇臂,Passage A,http:/www.racingheadservice.com/Company/RHS/RockerArms/RockerArms.aspx?AspxAutoDetectCookieSupport=1,Chromemoly (铬钼 ) steel rocker arms,Stamped rocker arms,http:/pitstopusa.com/i-5072027-comp-cams-magnum-steel-roller-rocker-arms-16-chevrolet-v8-265-40-rocker-stud-3-8-ratio-1-6.html,Manufactured: Stamped steel or hardened iron alloy Mounted on a stud with a pivot and nut,Passage A,DOHC / SOHC / OHV,Passage A,http:/auto.guser.cn/system/2010/03/001004004_67329_1.shtml,DOHC: 2 camshafts per head. Used on engines with 4 valves per cylinder. SOHC: Denotes a single shaft per head OHV: Camshaft is inside the engine block, for low speed engine,Passage A,New words （生词）,Camshaft Pushrod Lobe Cam Synchronize Critical Nickel Silicon Withstand Celsius,Stamp Stud Pivot Tip Recess Eliminate Intake / exhaust port Snap back Steel alloy Timing belt / chain,Passage A,Translation （翻译）,Page 26, Paragraph 4,Passage B,Variable Valve Timing （可变气门正时）,The camshaft uses rotating lobes that push against the valves to open and close them In high RPM condition, this configuration does not work well. When the intake valve opens right at the top of the intake stroke, it has a lot of trouble to get the air moving into the cylinder in a short time, such as in 4000 r/min condition. So the intake valve needs to open prior to the intake stroke in high RPM condition, compared with in low RPM condition The valves need to open and close differently in different engine speed-VVT,Background,Passage B,Variable Valve Timing （可变气门正时）,Variable Valve Timing and lifting Electronic Control Three cam lobes: two for low RPM, a third for high RPM,VTEC of Honda,http:/www.wiringdiagrams21.com/2009/03/15/honda-accord-vtec-engine-diagram-1994-1997,Passage B,Variable Valve Timing （可变气门正时）,Vario Cam (多变凸轮轴),Other VVT system,http:/forum.xitek.com/sorthread.php?threadid=496023,Passage B,Variable Valve Timing （可变气门正时）,MIVEC (Mitsubishi Innovative Valve Timing and Lift Electronic Control),Other VVT system,http:/forum.xitek.com/sorthread.php?threadid=496023,Passage B,Variable Valve Timing （可变气门正时）,VVT-i and VVTL-i : Toyota and Lexus engines VVL : Nissan engine, like VTEC VANOS : BMW engines, similar system in Ford, Lamborghini, Ferrari,Other VVT system,Passage B,New words （生词）,Activate Alternate Profile Swirl Driveability Retard Advance Pop Make sense Aggressive Transition,Groove Regular maintenance VVT Cam profile VTEC ECU MIVEC VVT-i VVTL-i VVL,Passage A,Classwork,Exercise 9,西华大学,XIHUA UNIVERSITY,交通与汽车工程学院,Faculty of Transportation and Automotive Engineering,Homework,Review the new word, especially the abbreviations,Exercise 3, 4, 5,西华大学,XIHUA UNIVERSITY,交通与汽车工程学院,Faculty of Transportation and Automotive Engineering,Thanks,